The is invention is that of pressure sensors and the invention relates more particularly to a cylinder pressure transmitter responsive to variations in pressure within a cylinder in an internal combustion engine during engine operation to provide an electrical control signal for use in regulating engine operation.
In a commonly assigned, copending patent application filed of even date herewith, Ser. No. 561,842 a cylinder pressure transmitter comprises means for mounting piezoelectric means in sealed relation to an engine cylinder to be responsive to variations in cylinder pressure during engine operation to provide initial electrical signals representative of pressure variations in the cylinder. That transmitter includes high temperature electronic means which are carried by the mounting means and which are electromagnetically shielded with the piezoelectric means within the mounting means for amplifying those initial signals to provide low impedance signals for transmission to computer control means or other signal processing means at a location remote from the cylinder. In that transmitter, the piezoelectric means preferably comprises a pair of piezoelectric discs which are polarized in opposite directions on opposite sides of a conductor electrode to generate the charge output from the discs in response to applied pressure and the discs are mounted against a flexible diaphragm with a selected preload compressive force to be responsive to pressure forces applied through the diaphragm.
However, it is found that such piezoelectric cylinder pressure transmitters are difficult to mass produce for use in commercial automotive applications.